EU officials say they will ask Spain to explain why police fired rubber bullets at migrants trying to swim to the Spanish territory of Ceuta.
Spain admitted that rubber bullets were fired, but said nobody was injured.
At least 14 people drowned on 6 February as hundreds of migrants attempted to reach the North African enclave from Morocco.
Together with a second Spanish enclave, Melilla, Ceuta represents the EU's only land border with Africa.
As a result the territories, both located along Morocco's Mediterranean coast, have become a magnet for migrants seeking work or asylum in Europe.
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